A light emitting device has a property to convert electric energy into photo energy. For instance, the light emitting device may represent various colors by adjusting the compositional ratio of compound semiconductors.
According to the related art, a transparent ohmic layer is formed on a light emitting structure including an N type GaN layer, an active layer and a P type GaN layer.
The transparent ohmic layer used in the light emitting device according to the related art mainly includes ITO-based oxides. Such metal oxides are transparent and have relatively superior electric conductivity so the metal oxides are used for an electrode contact layer of the light emitting device.
Recently, various studies and research have been performed in a nitride semiconductor light emitting device to manufacture a high-brightness LED. However, since there is possibility of depletion of indium (In), which is a main material of an ITO electrode extensively used in the related art, the cost of indium (In) is increased so that the manufacturing cost for the ITO electrode is increased. In addition, since the ITO electrode has no flexibility, the ITO electrode is not suitable for flexible devices.
In addition, the transparent ohmic layer used in the light emitting device needs to have superior light transparency and high surface-direction electric conductivity. However, according to the related art, there is no optimum transparent ohmic layer having a thin thickness and capable of increasing the surface-direction electric conductivity.
A nitride semiconductor light emitting device according to the related art represents various problems due to the lack of the optimum transparent ohmic layer, such as non-uniform current injection, low heat dissipation efficiency and low light extraction efficiency.
In addition, according to the related art, it is necessary to improve the light emitting efficiency and reliability of the light emitting device in order to implement high-power light emitting device. For instance, according to the related art, many attempts have been tried to improve the configuration of a light emitting structure that emits light, but the satisfied result is not obtained.